Process for the production of graphite powders of increased bulk density

ABSTRACT

The invention relates to a method for increasing the Scott density of synthetic and/or natural graphite powders of any particle size distribution, preferably of highly-pure graphite, by subjecting the graphite powder to an autogenous surface treatment. The inventive powder is used, in particular, for producing dispersions, coatings with an increased graphite/binder ratio and increased electric and thermal conductivity, gas and liquid-tight coatings on metal substrates, thermoplastic or duroplastic graphite-polymer composites, or for producing metallic, non-ferrous sintering materials.

This is a continuation of application Ser. No. 10/130,261, which wasaccepted as a filing under 35 U.S.C. 371 on Jul. 15, 2002 and which is a371 filing of PCT Application No. PCT/CH00/00514, filed Sep. 22, 2000,which claims priority to Swiss Application 2165/99, filed Nov. 26, 1999.All of these applications are incorporated herein by reference in theirentirety.

The present invention relates to a process for the production ofgraphite powders of increased bulk density. The present inventionrelates in particular to an autogenous surface treatment of anypulverulent graphitic materials, their bulk density and tamped densitybeing markedly increased and other important material properties beingadvantageously modified as a result of the mutual physical-mechanicalaction of the individual powder particles.

Graphitic materials, especially those with a high graphite content, areknown per se and are used in industry in a variety of ways. High-puritygraphitic carbons have xylene densities (also called single-crystaldensities or real densities) ranging from 1.80 to 2.27 g.cm⁻³ and acrystal structure which can be characterized by a c/2 value of 0.3354 to0.3360 nm and an L_(c) value of more than 40 nm (L_(c>)40 nm). Thesematerials are obtained from natural sources, enriched and purified orproduced synthetically from amorphous carbon products in a hightemperature process. Subsequent grinding processes produce pulverulentmaterials with different mean particle sizes in each case. A givenparticle size for a powder is normally always a mean value of a specificparticle size distribution. The particle size distribution to be usedfor a particular purpose depends especially on the composition of thegraphitic material and the associated properties, as well as on theintended use.

The particle shape is always platelet-like, the anisotropy of theparticles being the more pronounced the higher the xylene density andL_(c) values. The Scott density (also referred to as bulk density) ofsuch materials, for example with particle sizes smaller than 100 micron(particle size <100 μm, determined by laser diffraction analysis), isnormally below 0.25 g.cm⁻³, the Scott density being the lower thesmaller the particle size. Comminution of the particles by grindinggenerally results in a lowering of the Scott density. The Scott densitycan be somewhat increased by an optimized particle size distribution.Thus, for example, Scott densities up to max. 0.3 g.cm⁻³ are achieved byan optimized composition of fine and coarse fractions for such materialswith particle sizes below 100 micron.

The tamped density, the compressibility and the absorption capacity forpolymeric binder materials and liquids such as oils, and for organicsolvents and aqueous systems, are equally important properties ofgraphite powders. These properties correlate with the composition of thegraphite powders and especially with the particle size distribution. Ithas now been found that, surprisingly, the values of the Scott densityfor a particular graphite powder of any particle size distribution isconsiderably increased when the graphite powder is subjected to anautogenous surface treatment in which the particles impact with oneanother at an appropriate speed and for a sufficient length of time. Theimpacts and the associated mutual physical-mechanical action change thestructure or surface of the graphite particle in such a way as to resultin a considerable increase in the Scott density. The other propertiesmentioned above are also modified to a considerable extent.

Under the electron microscope, the crude, ground, platelet-like graphiteparticle has an irregular shape and sharp edges. The irregular particlecontours are abraded and the edges rounded off by the treatmentaccording to the invention. If the energy dose is appropriatelyoptimized, the grinding effect which occurs with other mechanicaltreatments, leading to a noticeable lowering of the bulk density, isconsiderably reduced or minimized. Although the abrasion of theparticles creates dust, which, together with a minimal grinding effect,leads to a slight reduction in particle size and Scott density (bulkdensity), this particle size effect is far outweighed by thesurprisingly large total increase in Scott density, and the change inthe other properties, caused by the treatment according to theinvention. The present invention can be at least partly explained by theobserved changes in the particle contours, but the invention is notbound to this explanation.

The present invention is defined in the Claims. In particular, thepresent invention relates to a process for increasing the Scott densityof graphite powders of any particle size distribution, characterized inthat the graphite powder is subjected to an autogenous surfacetreatment.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1A is a diagram of an apparatus for treating graphite particles.

FIG. 1B is an alternative view of the apparatus in FIG. 1A.

The process of autogenous surface treatment consists in allowing theindividual powder particles to impact with one another at a measuredspeed so that, as a result of the associated mutual physical-mechanicalaction of the individual particles, their surface structure changes butthe individual particle remains substantially unbroken, i.e. nosubstantial grinding effect occurs. This change in the particle contouror surface structure of the individual particle gives rise to theincrease in Scott density according to the invention. The autogenoussurface treatment is carried out, and the individual particles areallowed to act on one another, until the desired Scott density isachieved. The measured speed means that the speed or energy with whichthe individual particles are charged is adjusted so that the particlesdo not disintegrate on impact or collision, thereby practically avoidinga grinding effect. This adjustment is a question of process optimizationand does not present a problem to those skilled in the art.

The Scott density achievable by means of the optimized grinding effectfor a graphite powder of any particle size distribution can be increasedin each case by at least about 10% to about 100%, preferably by about20% to 80%, by the autogenous surface treatment according to theinvention. Hitherto unattained Scott densities of 0.45 g/cm³ or more arethus achieved for graphitic materials.

The tamped density achievable by means of the optimized grinding effectfor a graphite powder of any particle size distribution can also beincreased by at least about 10% to 100%, preferably by about 20% to 80%,by the process according to the invention. Hitherto unattained tampeddensities of at least 0.90 g/cm³ are thus achieved for graphite powders.

In the case of particle sizes of <100 μm, the autogenous surfacetreatment according to the invention is preferably carried out byfluidizing or dispersing the graphite powder particles in an inertcarrier gas and accelerating the particles with the aid of the carriergas, as described below. The intensity of this treatment is determinedby the carbon type and the mass of the particles, their speed and theamount of material used per treatment, i.e. the concentration of thefluidized particles dispersed in the gas. The intensity of the treatmentincreases with the softness of the graphitic carbon used, the mass ofthe particles, their speed and the amount used. For particle sizes of<300 μm, the dispersion and acceleration of the particles are preferablyeffected by means of rotating mechanical tools, for example in thepresent process by means of a turbine or directly by means of a rotatingdisk.

However, the grinding effect which occurs also increases simultaneouslywith increasing intensity of the treatment. Thus, to achieve the maximumbulk density of a material, there is a maximum intensity which resultsfrom the optimized parameters of particle speed, particle mass andamount used. The formation of agglomerates due to the agglutination ofsmaller particles, which would also lead to a sustained increase in theScott density, has not been observed. Treated particles larger than theuntreated particles used did not appear in any of the experimentsperformed. Analyses of the treated materials by scanning electronmicroscopy also showed no such agglomeration.

The treatment according to the invention not only increases the Scottdensity but also improves the compressibility properties of the graphitepowders and reduces their absorption capacity for polymeric bindermaterials and liquids such as oils, organic solvents and aqueoussystems. The crystallinity of the graphitic carbon particles, on theother hand, remains unaffected by the mechanical surface treatment. Thestructural parameters and the xylene density also remain unchangedcompared with the untreated particles.

The process according to the invention also increases the presseddensity achievable by the optimized grinding effect for a graphitepowder of any particle size distribution by at least about 0.5% to 10%,preferably by about 1% to 8%. If the powders treated according to theinvention are used to produce mouldings by compression under a pressureof 2.5 to/cm², markedly higher pressed densities can be achievedcompared with the untreated materials.

Furthermore, the powders treated according to the invention exhibit amarkedly reduced oil absorption capacity and binder uptake ranging fromabout 10% to 50% and especially from an average of about 20% to 45%,values in excess of 50% also being obtainable. This effect is achievedby the treatment according to the invention because the porosity (porestructure) of the particles is not affected by the treatment, as can bedemonstrated by the fact that the nitrogen adsorption properties andxylene densities hardly change.

Said markedly reduced absorption properties also result in markedlylower viscosities of dispersions of the graphite powders treatedaccording to the invention in liquid media, so dispersions with acorrespondingly increased solids content can be prepared with thegraphite powders treated according to the invention. The solids contentof liquid carbon dispersions can be increased by more than 5% to over30% by using graphite powders treated according to the invention.

Graphite powders suitable for the use according to the invention areespecially those with a high graphite content in the particle, andparticularly so-called high-purity graphites, preferably with xylenedensities ranging from 1.80 to 2.27 g.cm⁻³ and a crystal structurecharacterized by a c/2 value of 0.3354 to 0.3360 nm and an L_(c) valueof more than 40 nm (L_(c>)40 nr). The powders can be obtained fromnatural sources or prepared synthetically from amorphous carbon productsand can have any mean particle size and particle size distribution.Preferred pulverulent graphitic materials are those with a mean particlesize of up to 150 μm, preferably of 1 μm to 50 μm, and especiallyhigh-purity pulverulent graphites. Such graphites are known per se.

The process according to the invention is preferably carried out in sucha way that the graphite powder particles to be treated are dispersed andfluidized in a gas. This can be done using any method of fluidizationtechnology known per se in which the particles impact with one anotherin the fluidized state and thereby change their surface contours andsurface structures, as is the case e.g. in a fluidized bed. However, tocarry out the process according to the invention, the fluidizedparticles are preferably provided with higher speeds so that theparticles fluidized in this way are accelerated with higher energies.Preferably, the fluidized particles are continuously concentrated anddiluted again in the gaseous environment. The resulting collisionsbetween the particles set in rotation, and the friction between them,result in surface abrasion of the particles, the energy transferred tothe particles being adjusted so that the collisions and friction causesubstantially no disintegration of the particles.

The process according to the invention can be put into optimum effecte.g. in the device shown in FIGS. 1A and 1B. This device consistsspecifically of a circular disk 100 with radial impact pins 101flush-mounted on the rim, said disk being sheathed by a cylindricaltreatment chamber 110 closed to the outside (turbine with associatedturbine effect). The dimensions of the cylindrical treatment chamber 110are adjusted so that it encloses the disk 100 and can allow some spacebetween its inner wall and the rotating disk 100. The disk 100 isconnected to a motor 160, located outside the treatment chamber 110, bymeans of a shaft 150 through the wall of the treatment chamber and canbe set in rotation by this motor 160. The cylindrical treatment chamberis provided with a radial aperture 111 (hole). An additional aperture112 (hole) is provided in the cylinder jacket of the treatment chamber110, perpendicular to the disk and disk axis. Apertures 111 and 112 areconnected by a tube 120 located outside the treatment chamber. Thus tube120 running outside the treatment chamber 110 and attached to the wallof the treatment chamber 110, connects the periphery of the treatmentchamber 110 to its centre. The gas (fluid) containing the fluidizedparticles, accelerated centrifugally by the rotating disk 100,circulates through this external treatment tube 120, exiting through thetube at the periphery of the treatment chamber 110 as a result of thecentrifugal force and flowing back through the other end of this tubeinto the centre of the treatment chamber 110, where it is acceleratedagain. The particles of material are accelerated by the impact pins 101of the rotating disk 100 and driven away in a peripheral direction bythe centrifugal forces produced by the high-speed rotor. The particlesdispersed and accelerated into the gas in this way circulate in themachine along the inside of the cylinder jacket. The particles reachingthe inlet of the circulation tube, input 130 enter the tube and returnto the treatment chamber in the region of the centre of the machine.This results in a continuous concentration and dilution of the particlesin the surrounding gaseous medium. A fraction of the treated particlesis continuously fed into input 130 or withdrawn from an attached tube,output 140, but the process can also be carried out as a batch process.The graphite powders treated according to the invention canadvantageously be used as pigments in aqueous or solvent-baseddispersions, thereby achieving higher solids contents than withuntreated powders. The viscosity of liquid dispersions of materialstreated according to the invention is markedly lower for the same solidscontent. Also, when dispersions according to the invention are appliedto substrates and dried, coatings with markedly lower porosity valuesare obtained because the content of liquid phase is markedly lower. Thehigher solids content also means that smaller binder/carbon ratios areneeded to stabilize a dried carbon coating on a substrate. The lowpolymeric binder contents result in a marked increase in the electricaland thermal conductivities of such carbon layers.

Dispersions containing mixtures of synthetic and/or natural graphiticcarbons treated according to the invention and a polymeric binder in anaqueous or solvent-based medium can be applied to metal foils and driedto give stable coatings (for thicknesses of 10 to 5000 μm) with anincreased graphite/binder ratio and hence also increased electrical andthermal conductivities. The porosities of the dried films are normallybelow 50% and are thus appreciably lower than those of films formed ofconventional graphites. Such dispersions can therefore advantageouslyalso be used for gas-tight and liquid-tight coatings on metalsubstrates, which can be used as electrically conducting anticorrosivefilms on metal foils and plates.

The dried coatings formed by the graphites treated according to theinvention can be compressed by a calender without the graphite filmdelaminating from the metal foil. This delamination from the metal foilis frequently observed with untreated graphites. The calendering ofgraphite films produced from graphite powders treated according to theinvention affords coatings with porosities below 30% without alteringthe texture or particle structure of the graphite powders used. Suchfilm coatings on metal foils, characterized by porosities below 30% andstabilized with lower binder/carbon ratios, can be used in lithium ionbatteries as negative electrodes with charge densities above 550 Ah/l.The current-carrying capacity of such electrodes is markedly higher thanthat of electrodes made of conventional graphite powders. Such negativeelectrodes can thus be used very advantageously for lithium ion cellswith a high power density.

The high packing density of the synthetic or natural graphites treatedaccording to the invention, combined with the relatively low polymericbinder absorption capacity, is advantageous in the production ofgraphite/polymer composites which can be compressed to gas-tightgraphite plates of high electrical conductivity. Such plates areadvantageously used as bipolar plates in polymer electrolyte fuel celltechnology.

Mixtures of polymers with synthetic or natural graphites or graphiticcarbons treated according to the invention form thermoplastic orthermosetting composites with a higher proportion of carbon filler and alower processing viscosity: Thermoplastic polymer/graphite compositematerials with graphites treated according to the invention have higher(and hence improved) values in respect of their isotropic, mechanical,thermal and electrical properties and behave more isotropically thancomposites with untreated graphitic carbons.

Metallic non-ferrous sintered materials which have been produced withsynthetic or natural graphitic carbons treated according to theinvention, or contain such carbons, have improved isotropic, mechanicaland tribological properties.

The Examples which follow describe the invention.

Examples 1 to 6 show the material properties of various graphites beforeand after the autogenous surface treatment according to the invention.The experiments were performed in the device described in the abovesection. The rotating disk used had a periphery of 0.75 m and a speed ofrotation of 4800 rpm.

Examples 1-6 were carried out under the experimental conditions given inTable 1. TABLE 1 Type of Speed of Example graphite Amount used Treatmenttime rotating disk 1 TIMREX ® 150 g 5 min 4800 rpm KS-graphite 2TIMREX ® 150 g 5 min 4200 rpm SLX-graphite 3 TIMREX ® 150 g 5 min 4800rpm SLM-graphite 4 TIMREX ® 200 g 5 min 4800 rpm SFG-graphite 5 TIMREX ®200 g 7 min 4800 rpm NP-graphite 6 TIMREX ® 200 g 5 min 4800 rpm KS 5-75TTTIMREX ® KS-graphite = TIMREX ® KS 5-25 from TIMCAL AGTIMREX ® SLX-graphite = TIMREX ® SLX 50 from TIMCAL AGTIMREX ® SLM-graphite = TIMREX ® SLM 44 from TIMCAL AGTIMREX ® SFG-graphite = TIMREX ® SFG 44 from TIMCAL AGTIMREX ® NP-graphite = TIMREX ® NP 44 from TIMCAL AG

Examples 1 to 6 show a marked increase in Scott density (bulk density)and tamped density for the powders treated according to the invention.The treated powders exhibited no agglomerates whatsoever. The resultingchange in particle size distribution is indicative of a small grindingeffect. The slight lowering of d values, however, is caused especiallyby the dust produced by the abrasion of the particles. The porestructure of the treated particles is not affected by the surfacetreatment. It is assumed that the dust produced by the treatment and theslight decrease in particle size distribution are the main reason forthe slight lowering of the L_(c) values and the xylene densities. Theelastic recovery of the compressed treated materials drops sharply. Thepressed density of mouldings produced from the treated materials under apressure of 2.5 to/cm² increases sharply. Although the BET values areincreased somewhat, the oil absorption and binder absorption of theparticles treated according to the invention decrease markedly.Dispersions of treated carbon particles in liquid media exhibit markedlylower viscosities than dispersions of untreated carbon particles. Thesolids content of liquid carbon dispersions can be increased by morethan 5% by using carbon particles according to the invention. Theelectrical resistance of the carbons treated according to the inventionincreases. The changes in surface contours of the individual particleswhich result from the treatment of powders according to the inventioncan be clearly seen from scanning electron micrographs.

Experimental Section

The particle size distribution of the materials was determined by laserdiffraction analysis using a MALVERN Mastersizer. The structuralparameters were obtained from X-ray diffraction experiments based on theCuK_(α1) line. The crystallographic cell constant in the c direction(c/2) was determined from the relative position of the (002) or (004)diffraction reflex. The maximum height of the single-crystal domains ina particle in the crystallographic c direction, L_(c), and the resultingnumber of ideally stacked graphite planes were obtained from the (002)or (004) diffraction reflex according to the model of Scherrer and Jones(P. Scherrer, Göttinger Nachrichten 2 (1918) p. 98; F. W. Jones, Proc.Roy. Soc. (London) 166 A (1938) p. 16). The xylene density wasdetermined according to DIN 51 901. Determination of the Scott densitywas based on ASTM B 329. The tamped density was determined according toAKK-19. The specific surface areas were determined by the method ofBrunauer, Emmett and Teller using a Micromeritics ASAP 2010. Todetermine the elastic recovery, the material was placed under a pressureof 0.5 to/cm². The recovery was obtained from the height of the mouldingwith and without applied pressure and is given in percent. Theelectrical resistance was measured according to DIN 51 911 using amoulding produced under a pressure of 2.5 to/cm². The pressed density ofthis moulding is also given. The oil absorption was measured on thebasis of DIN ISO 787 with initial weights of 0.5 g of material and 1.5 gof oil. The mixture was centrifuged in a Sigma 6-10 centrifuge for 90min at a speed of 1500 rpm.

EXAMPLE 1

TIMREX ® KS synthetic graphite TIMREX ® KS synthetic graphite UntreatedAfter treatment Particle size Particle size d₁₀ = 7.0 micron d₁₀ = 5.9micron d₅₀ = 15.2 micron d₅₀ = 13.5 micron d₉₀ = 30.2 micron d₉₀ = 27.4micron L_(c)(002)/L_(c)(004) L_(c)(002)/L_(c)(004) 120 nm/68 nm 101nm/64 nm c/2 (002)/c/2 (004) c/2 (002)/c/2 (004) 0.3355 nm/0.3355 nm0.3355 nm/0.3355 nm Xylene density Xylene density 2.254 g · cm⁻³ 2.248 g· cm⁻³ Scott density Scott density 0.23 g · cm⁻³ 0.30 g · cm⁻³ Tampeddensity Tamped density 0.539 g · cm⁻³ 0.674 g · cm⁻³ BET specificsurface area BET specific surface area 8.6 m² · g⁻¹ 9.3 m² · g⁻¹ Elasticrecovery Elastic recovery 17% 12.3% Electrical resistance Electricalresistance 1.911 mΩ · cm 2.085 mΩ · cm Oil absorption Oil absorption113.5% ± 1.3% 64.3% ± 0.2% Pressed density (2.5 to/cm²) Pressed density(2.5 to/cm²) 1.863 g · cm⁻³ 1.957 g · cm⁻³

EXAMPLE 2

TIMREX ® SLX synthetic graphite TIMREX ® SLX synthetic Untreatedgraphite After treatment Particle size Particle size d₁₀ = 11.6 micrond₁₀ = 7.4 micron d₅₀ = 27.3 micron d₅₀ = 20.4 micron d₉₀ = 52.5 micrond₉₀ = 40.8 micron L_(c)(002)/L_(c)(004) L_(c)(002)/L_(c)(004) >500nm/232 nm 368 nm/158 nm c/2 (002)/c/2 (004) c/2 (002)/c/2 (004) 0.3354nm/0.3354 nm 0.3354 nm/0.3354 nm Xylene density Xylene density 2.261 g ·cm⁻³ 2.258 g · cm⁻³ Scott density Scott density 0.30 g · cm⁻³ 0.38 g ·cm⁻³ Tamped density Tamped density 0.641 g · cm⁻³ 0.778 g · cm⁻³ BETspecific surface area BET specific surface area 4.0 m² · g⁻¹ 5.9 m² ·g⁻¹ Elastic recovery Elastic recovery 7.7% 4.6% Electrical resistanceElectrical resistance 0.986 mΩ · cm 1.166 mΩ · cm Oil absorption Oilabsorption 94.7% ± 11.9% 73.3% ± 1.9% Pressed density (2.5 to/cm²)Pressed density (2.5 to/cm²) 2.036 g · cm⁻³ 2.051 g · cm⁻³

EXAMPLE 3

TIMREX ® SLM synthetic TIMREX ® SLM synthetic graphite Untreatedgraphite After treatment Particle size Particle size d₁₀ = 7.3 micrond₁₀ = 4.3 micron d₅₀ = 23.2 micron d₅₀ = 13.9 micron d₉₀ = 49.4 micrond₉₀ = 35.0 micron L_(c)(002)/L_(c)(004) L_(c)(002)/L_(c)(004) 241 nm/139nm 196 nm/116 nm c/2 (002)/c/2 (004) c/2 (002)/c/2 (004) 0.3354nm/0.3354 nm 0.3354 nm/0.3354 nm Xylene density Xylene density 2.254 g ·cm⁻³ 2.252 g · cm⁻³ Scott density Scott density 0.19 g · cm⁻³ 0.34 g ·cm⁻³ Tamped density Tamped density 0.408 g · cm⁻³ 0.738 g · cm⁻³ BETspecific surface area BET specific surface area 4.9 m² · g⁻¹ 7.7 m² ·g⁻¹ Elastic recovery Elastic recovery 14.0% 8.6% Electrical resistanceElectrical resistance 1.278 mΩ · cm 1.741 mΩ · cm Oil absorption Oilabsorption 109.5% ± 2.7% 75.0% ± 5.3% Pressed density (2.5 to/cm²)Pressed density (2.5 to/cm²) 1.930 g · cm⁻³ 2.036 g · cm⁻³

EXAMPLE 4

TIMREX ® SFG synthetic TIMREX ® SFG synthetic graphite Untreatedgraphite After treatment Particle size Particle size d₁₀ = 7.5 micrond₁₀ = 4.4 micron d₅₀ = 24.1 micron d₅₀ = 15.0 micron d₉₀ = 49.2 micrond₉₀ = 35.5 micron L_(c)(002)/L_(c)(004) L_(c)(002)/L_(c)(004) 320 nm/138nm 283 nm/199 nm c/2 (002)/c/2 (004) c/2 (002)/c/2 (004) 0.3354nm/0.3354 nm 0.3354 nm/0.3354 nm Xylene density Xylene density 2.262 g ·cm⁻³ 2.258 g · cm⁻³ Scott density Scott density 0.20 g · cm⁻³ 0.36 g ·cm⁻³ Tamped density Tamped density 0.420 g · cm⁻³ 0.766 g · cm⁻³ BETspecific surface area BET specific surface area 5.9 m² · g⁻¹ 7.4 m² ·g⁻¹ Elastic recovery Elastic recovery 9.2% 5.6% Electrical resistanceElectrical resistance 0.925 mΩ · cm 0.986 mΩ · cm Oil absorption Oilabsorption 110.2% ± 6.4% 81.8% ± 6.9% Pressed density (2.5 to/cm²)Pressed density (2.5 to/cm²) 2.005 g · cm⁻³ 2.036 g · cm⁻³

EXAMPLE 5

TIMREX ® NP TIMREX ® NP purified natural graphite purified naturalgraphite Untreated After treatment Particle size Particle size d₁₀ = 6.6micron d₁₀ = 3.7 micron d₅₀ = 23.0 micron d₅₀ = 13.8 micron d₉₀ = 49.5micron d₉₀ = 36.9 micron L_(c)(002)/L_(c)(004) L_(c)(002)/L_(c)(004) 364nm/166 nm 255 nm/103 nm c/2 (002)/c/2 (004) c/2 (002)/c/2 (004) 0.3354nm/0.3354 nm 0.3354 nm/0.3354 nm Xylene density Xylene density 2.263 g ·cm⁻³ 2.258 g · cm⁻³ Scott density Scott density 0.24 g · cm⁻³ 0.42 g ·cm⁻³ Tamped density Tamped density 0.495 g · cm⁻³ 0.862 g · cm⁻³ BETspecific surface area BET specific surface area 5.0 m² · g⁻¹ 7.9 m² ·g⁻¹ Elastic recovery Elastic recovery 4.9% 3.8% Electrical resistanceElectrical resistance 0.910 mΩ · cm 1.359 mΩ · cm Oil absorption Oilabsorption 107.2% ± 3.6% 58.9% ± 0.6% Pressed density (2.5 to/cm²)Pressed density (2.5 to/cm²) 2.066 g · cm⁻³ 2.064 g · cm⁻³

EXAMPLE 6

TIMREX ® KS TIMREX ® KS purified natural graphite purified naturalgraphite Untreated After treatment Particle size Particle size d₁₀ = 8.3micron d₁₀ = 3.1 micron d₅₀ = 38.4 micron d₅₀ = 38.4 micron d₉₀ = 68.4micron d₉₀ = 68.4 micron L_(c)(002)/L_(c)(004) L_(c)(002)/L_(c)(004) 142nm/62 nm 105 nm/52 nm c/2 (002)/c/2 (004) c/2 (002)/c/2 (004) 0.3355nm/0.3355 nm 0.3356 nm/0.3356 nm Xylene density Xylene density 2.227 g ·cm⁻³ 2.225 g · cm⁻³ Scott density Scott density 0.44 g · cm⁻³ 0.46 g ·cm⁻³ Tamped density Tamped density 0.84 g · cm⁻³ 0.902 g · cm⁻³ BETspecific surface area BET specific surface area 4.1 m² · g⁻¹ 8.0 m² ·g⁻¹ Elastic recovery Elastic recovery 25% 14.68% Electrical resistanceElectrical resistance 2.109 mΩ · cm 2.311 mΩ · cm Oil absorption Oilabsorption 97.2% ± 1.6% 54.7% ± 0.8% Pressed density (2.5 to/cm²)Pressed density (2.5 to/cm²) 1.912 g · cm⁻³ 1.972 g · cm⁻³

1-15. (canceled)
 16. A process for increasing the pressed density of astarting graphite powder of any particle size distribution, the startinggraphite powder chosen from synthetic graphitic carbon and naturalgraphitic carbon wherein the starting graphite powder has a highgraphite content in the particle, comprising subjecting the startinggraphite powder to an autogenous surface treatment in which individualgraphite powder particles are allowed to impact with one another at ameasured speed so that their surface structure changes whilesubstantially retaining graphite particle shape without a substantialgrinding effect occurring and wherein said autogenous surface treatmentis carried out until the pressed density of the starting material hasincreased by at least about 0.5% to 10%
 17. The process according toclaim 16 wherein the graphite powder is high-purity graphite.
 18. Theprocess according to claim 16 wherein the graphite powder has a xylenedensity ranging from 1.80 to 2.27 g/cm³, a crystal structurecharacterized by a c/2 value of 0.3354 to 0.3360, and an L_(c) value ofmore than 40nm (L_(c>)40nm).
 19. The process according to claim 16wherein the graphite powder has a particle size of up to 150 μm.
 20. Theprocess according to claim 19 wherein the graphite powder has a particlesize of 1 pm to 50 μm.
 21. The process according to claim 16 wherein theautogenous surface treatment is carried out until the pressed density ofthe starting graphite powder has increased by about 1% to 8%.
 22. Theprocess according to claim 16 wherein the autogenous surface treatmentis carried out by fluidizing or dispersing graphite powder particleswith sizes of <100 μm in an inert carrier gas with the aid of a carriergas.
 23. The process according to claim 16 wherein the autogenoussurface treatment is carried out by dispersing graphite powder particleswith sizes of <300 μm by means of a rotating mechanical tool.
 24. Theprocess according to claim 23 wherein the rotating mechanical tool is aturbine.
 25. A process for decreasing the absorption capacity of astarting graphite powder of any particle size distribution, the startinggraphite powder chosen from synthetic graphitic carbon and naturalgraphitic carbon wherein the starting graphite powder has a highgraphite content in the particle, comprising subjecting the startinggraphite powder to an autogenous surface treatment in which individualgraphite powder particles are allowed to impact with one another at ameasured speed so that their surface structure changes whilesubstantially retaining graphite particle shape without a substantialgrinding effect occurring and wherein said autogenous surface treatmentis carried out until the absorption capacity of the starting materialhas decreased by at least about 10% to 50%.
 26. The process according toclaim 25 wherein the graphite powder is high-purity graphite.
 27. Theprocess according to claim 25 wherein the graphite powder has a xylenedensity ranging from 1.80 to 2.27 g/cm³, a crystal structurecharacterized by a c/2 value of 0.3354 to 0.3360, and an L_(c) value ofmore than 40 nm (L_(c>)40 nm).
 28. The process according to claim 25wherein the graphite powder has an average particle size of up to about150 μm.
 29. The process according to claim 28 wherein the graphitepowder has an average particle size of about 1 μm to 50 μm.
 30. Theprocess according to claim 25 wherein the autogenous surface treatmentis carried out until the absorption capacity of the starting graphitepowder has increased by about 20% to 45%.
 31. The process according toclaim 25 wherein the autogenous surface treatment is carried out byfluidizing or dispersing graphite powder particles with sizes of <100 μmin an inert carrier gas with the aid of a carrier gas.
 32. The processaccording to claim 25 wherein the autogenous surface treatment iscarried out by dispersing graphite powder particles with sizes of <300μm by means of a rotating mechanical tool.
 33. The process according toclaim 32 wherein the rotating mechanical tool is a turbine.
 34. Anapparatus for treating graphite particles comprising a cylindricalchamber comprising a base and a curved face, the cylindrical chamberfurther comprising a first aperture for graphite particles exiting thecylindrical chamber; a second aperture for graphite particles enteringthe cylindrical chamber; an internal disk for accelerating the graphiteparticles, having a diameter less than the inner diameter of thecylindrical chamber wherein the disk further comprises one or moreimpact pins and a rim; a motor for rotating the internal disk; a shaftfor connecting the motor and the internal disk; and a tube forcirculating graphite particles from the first aperture to the secondaperture, further comprising an external input for adding graphiteparticles to the tube and an external output for removing graphiteparticles from the tube.
 35. The apparatus of claim 34 wherein the firstaperture is located on the curved face of the cylindrical chamber. 36.The apparatus of claim 34 wherein the second aperture located on thebase of the cylindrical chamber.
 37. The apparatus of claim 36 whereinthe second aperture is located at about the center of the base of thecylindrical chamber.
 38. The apparatus of claim 34 wherein the impactpins are mounted flush with the rim of the internal disk and extendtowards the center of the internal disk.
 39. The apparatus of claim 38wherein the length of the impact pins are less than the radius of theinternal disk.
 40. The apparatus of claim 39 wherein the impact pins arelocated on a single face of the internal disk.
 41. The apparatus ofclaim 40 wherein the impact pins are located on the face of the internaldisk nearest to the second aperture.
 42. The apparatus of claim 41wherein the internal disk has a periphery of about 0.75m.
 43. Theapparatus of claim 34 wherein the motor rotates the internal disk atabout 4800 rpm.
 44. The apparatus of claim 34 wherein the graphiteparticles are added to the tube through the external input and removedfrom the circulation tube through the external output continuously. 45.A graphite powder subjected to the process of claim 16 or 25, having atleast one property chosen from increased bulk density, decreasedabsorption capacity, and increased pressed density.
 46. A graphitematerial with an average particle size of about 14 micron having a Scottdensity of about 0.30 g.cm⁻³; a tamped density of about 0.674 g.cm⁻³; adibutyl phthalate (DBP) oil absorption of about 64 g DBP/100 g graphite;and a pressed density of about 1.957 g.cm⁻³.
 47. A graphite materialwith an average particle size of about 20 micron having a Scott densityof about 0.38 g.cm⁻³; a tamped density of about 0.778 g.cm⁻³; a dibutylphthalate (DBP) oil absorption of about 73 g DBP/100 g graphite; and apressed density of about 2.051 g.cm⁻³.
 48. A graphite material with anaverage particle size of about 14 micron having a Scott density of about0.34 g.cm⁻³; a tamped density of about 0.738 g.cm⁻³; a dibutyl phthalate(DBP) oil absorption of about 75.0 g DBP/100 g graphite; and a presseddensity of about 2.036 g.cm⁻³.
 49. A graphite material with an averageparticle size of about 15 micron having a Scott density of about 0.36g.cm⁻³; a tamped density of about 0.766 g.cm⁻³; a dibutyl phthalate(DBP) oil absorption of about 81.8 g DBP/100 g graphite; and a presseddensity of about 2.036 g.cm⁻³.
 50. A graphite material with an averageparticle size of about 14 micron having a Scott density of about 0.42g.cm⁻³; a tamped density of about 0.862 g.cm⁻³; a dibutyl phthalate(DBP) oil absorption of about 58.9 g DBP/100 g graphite; and a presseddensity of about 2.064 g.cm⁻³.
 51. A graphite material with an averageparticle size of about 38 micron having a Scott density of about 0.46 gcm⁻³; a tamped density of about 0.902 g.cm⁻³; a dibutyl phthalate (DBP)oil absorption of about 54.7 g DBP/100 g graphite; and a pressed densityof about 1.972 g.cm⁻³.
 52. A graphite material having a Scott density ofabout 0.45 g/cm³ or greater.
 53. A graphite material having a tampeddensity of about 0.90 g/cm³ or greater.
 54. A liquid dispersioncomprising a detectable amount of at least one graphite material of anyone of claims 46 to 53 and a liquid.
 55. The liquid dispersion of claim54, having an increased solids content.
 56. The liquid dispersion ofclaim 55, wherein the solids content is increased by about 5% to about30%.
 57. A coating on a metallic substrate, the coating comprising adetectable amount of at least one graphite material of claim 45 and apolymeric binder.
 58. A negative electrode of a lithium ion batterycomprising the coating of claim
 57. 59. A lithium ion battery comprisingthe negative electrode of claim
 58. 60. A composite comprising athermoplastic or thermosetting polymer and a detectable amount of atleast one graphite material of claim
 45. 61. The composite of claim 60,compressed to provide a graphite plate of high electrical conductivity.62. An electrolyte fuel cell, comprising the graphite plate of claim 61as a bipolar plate.
 63. A metallic sintered material comprising adetectable amount of at least one graphite material of claim 45 whereinthe metallic sintered material is substantially free of iron.